Barcelona, 2000: Oasis have cancelled a gig, not because of anything to do with Liam or Noel Gallagher, but because drummer Alan White has hurt his arm. With the band out drinking in their downtime, singer Liam oversteps the mark with brother Noel, the group's guitarist and chief songwriter, going much further than the fraternal banter, mickey-taking and occasional outbreak of hostilities that has defined their relationship since the band formed in 1991. He questions the legitimacy of Anais, Noel's daughter by his former wife, Meg Mathews.

Noel is on top of Liam in an instant, punching him, splitting his lip. Afterwards, Noel leaves the tour, the rest of the band dragging themselves around Europe without him. But he does not leave for good. "I've never forgiven him because he's never apologised," said Noel in 2005, talking about the incident for the first time in Q magazine, the five-year silence on the matter an indication of the seriousness of the schism it opened between two people who had been at loggerheads since growing up together, sharing a bedroom in Burnage, Manchester. "He's my brother. I hope he's reading this and realises that. He's my brother but he's at arm's length until he apologises for what he's done."

Liam did apologise eventually and the pair patched things up, as they have done with every big bust-up since Liam hit Noel over the head with a tambourine on stage in Los Angeles in 1994, during their first US tour. Not for the last time, Noel threatened to call it a day.

He didn't of course. This time, though, his departure from a group who've spent the best part of two decades as the biggest in Britain is final, with 42-year-old Noel this time saying goodbye following a pre-gig row backstage in Paris on Friday night, minutes before the band were due to headline the Rock en Seine festival. There was no blood, but 36-year-old Liam is reported to have broken one of Noel's guitars during the fracas.

A spokesperson for the band declined to comment beyond the statement from Noel that quickly appeared on the official Oasis website: "It's with some sadness and great relief to tell you that I quit Oasis tonight. I simply could not go on working with Liam a day longer."

By Saturday afternoon there seemed no doubt in the elder Gallagher's mind as he updated with a more substantial explanation. "The details are not important and of too great a number to list. But I feel you have the right to know the level of verbal and violent intimidation towards me, my family and friends and comrades has become intolerable," he said. "The lack of support and understanding from my management and band mates has left me with no other option than to get me cape and seek pastures new."

It is the "great relief" part of Noel's statement that is telling. In the past the Gallaghers had, like many highly successful rock stars who don't always get on, managed to maintain at least a working relationship in order to keep what remains a very lucrative show on the road. Even if much of the attendant compromise often seemed to be on the part of the level-headed, pragmatic Noel, the band's commander-in-chief. "People don't see what I've had to put up with for 30-odd years," Noel has said. "But also they don't see that if we keep the right distance it really works."

Superficially, this has been true of late. The band's current tour has been their biggest. Their last two albums, 2005's Don't Believe the Truth and last year's Dig Out Your Soul, have earned the best critical notices since their mid-90s peak.

While designed to keep the peace, keeping their distance may also have been part of the problem, enabling trouble to bubble up without being properly dealt with. Once the Gallaghers seemed to communicate, as brothers sometimes do, through face-to-face flare-ups. Interviewed together, they would egg each other on, aware that this was what even people who weren't Oasis fans were keen to read. (Or hear, with 1995's classic Wibbling Rivalry CD of Noel and Liam in a highly amusing interview with author and journalist John Harris definitely worth tracking down, especially now.)

"The first time I interviewed them it was clear that Noel was funny, but the sensible one, who knew when to keep his mouth shut," says Q journalist Michael Odell, who has spoken to Liam and Noel at least half a dozen times in recent years, and to whom Noel revealed the truth behind the Barcelona walkout. "Liam was wading in on Patsy Kensit and it was noticeable later on that Noel decided to play along, and they were unleashing volleys about everyone after that."

It has been hard to conclude that they talk much at all, except via the press. Perhaps it's just hindsight but, despite official insistence that whispers of a rift were nonsense, that it was actually business as usual, Oasis-style, the familiar Gallagher ding-dong quotes from the past few months' interviews seem to indicate something more aggressive.

"I don't like Liam," Noel again told Q in March, while revealing that even though both have wives and children, they almost never spend traditional family time together, suggesting a more fundamental aspect to the estrangement. There was further proof of this when Liam replied through the pages of the NME, announcing, "It takes more than blood to be my brother", and declaring: "He doesn't like me and I don't like him." Perhaps Noel summed up his position most succinctly back in February when he declared: "I am eternally spring but my brother Liam is like the blackest winter ever."

Noel has said it was Liam's drinking that often broke the detente, that tipped him over from funny to mean. It's unclear whether this was behind this latest falling out, but that seems unlikely – Liam has been on a health kick recently. Perhaps, as his statement suggests, Noel has simply had it with playing nice for the sake of the greater good. "Noel is the guy who's chained to the Tasmanian devil," says Danny Eccleston, consultant editor of Mojo. "A lifetime of that would wear you down. He's a smart guy, he's knows there's no Oasis without either of them. But maybe he's had enough now."

You can't say they haven't tried, though, to the extent that those around them have suffered while the pair attempted to work out their differences at epic length, with three drummers, two wives, a guitarist and a bassist left behind along the way. "It's a dysfunctional relationship where everyone else is a casualty," says Q's Michael Odell.

Now it seems they have grown too far apart to stomach even working together. In February 2008, while the band were finishing Dig Out Your Soul in Los Angeles, Liam disappeared back home for the weekend, marrying long-term partner Nicole Appleton without telling his colleagues, or inviting his brother, for fear it would all end up in the tabloids. "They had a major unreported bust-up that resulted in a couple of tracks not making it on the album, because Liam hadn't done his vocals," says author and Mojo journalist Pat Gilbert, who joined the band on tour last autumn. "I rarely saw them together then. Liam was living a completely separate life to the band."

There have also been hints of differences over the direction of the band, with conflict on the first day of recording Dig Out Your Soul as Liam reacted badly to the presence of keyboards, which might embellish the band's sound.

"He has an irrational fear of keyboards," explained Noel later. "This is the man who thought we had gone too dance when I wrote 'Wonderwall'because the drums didn't go boom-boom bap, boom-boom bap. Liam is very institutionalised by being in Oasis."

As the band's creative engine room, Noel has been sensitive to charges that the brothers have not evolved at the same rate as their peers, such as Blur's Damon Albarn or Radiohead. Liam isn't quite so bothered. "He's happy for them to be a tribute to their past," says Odell.

Initially long-term Oasis watchers were loth to jump to conclusions in the aftermath of Friday night, but it seems as if Noel now recording his often mooted solo album and Liam perhaps spending more time modelling his new line of smart casual clothing, Pretty Green, is where things are headed. In the past the brothers have always somehow managed to reconcile. "They probably will work together again eventually," said Alan McGee, who signed the band to his Creation label and knows their ups and downs better than most.

It certainly remains hard to imagine one on stage without the other, but Noel Gallagher, never a man to back down if he feels he is right, now seems set on a future without his brother. Oasis are no more, in fact they're already consigned to the past in the mind of the man who steered the ship. "I would like to thank all the Oasis fans, all over the world," Noel's second statement concluded. "The last 18 years have been truly, truly amazing… a dream come true. I take with me glorious memories. Now if you excuse me, I have a family and football team to indulge. I'll see you somewhere down the road."

Sibling rivalry and brotherly love

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Barry and Robin Gibb of the Bee Gees became so estranged that they resorted to making separate TV appearances to denounce each other. Robin walked out in 1969 but came back the following year.

The Everly brothers didn't speak to each other for 10 years and the Kinks' Ray and Dave Davies had a punch-up on stage.

The Proclaimers, Celtic soul twin brothers Craig and Charlie Reid, are still playing together happily since forming their band in 1983.

Radiohead's brothers, Jonny and Colin Greenwood, talk of each other in interviews with affection.

The Kings of Leon are three brothers and a cousin. Nashville preacher's sons Jared, Caleb and Nathan Followill have played together since 1999.